Method for repairing, waterproofing, insulating, reinforcing, restoring of wall systems

ABSTRACT

A method for repairing and/or waterproofing and/or insulating and/or reinforcing and/or restoring the structural integrity of wall systems, which it consists in providing spaced injection holes within a wall system in a manner suitable to pass through cavities that exist in the wall system, inserting injection tubes in these holes, and then inserting a substance that expands after injection as a consequence of a chemical reaction so that the substance reaches the cavities connected to the injection holes or are proximate thereto, the injection tubes being, preferably gradually retracted along the injection holes in the opposite direction with respect to insertion, to allow the substance diffusing in cavities crossed by the injection holes or proximate thereto.

The present invention relates to a method for repairing and/orwaterproofing and/or insulating and/or reinforcing and/or restoring thestructural integrity of wall systems. In particular, the methodaccording to the invention is capable of increasing the mechanicalstrength of a wall system and/or of decreasing its permeability to flowsof water and/or of reducing its thermal conductivity and/or otherproperties and can be performed even in the presence of water.

BACKGROUND OF THE INVENTION

Walls or wall systems that constitute buildings are generally producedby superimposing or arranging side by side blocks of stone or brick orother materials, with the interposition of a binder based on lime orcement or other binding materials, without the presence of voids orcavities.

Usually design sizing of such buildings is carried out in fact byconsidering the entire cross-section of the wall system as reactive,i.e., it is assumed that all of the cross-section of the masonry isinvolved in the support of the overlying loads; in other words, thepresence of voids or cavities inside the wall system is excluded. Interms of strength, the design takes into account an allowable tensionfor the masonry that is determined by the contribution provided by thestrength of the block of brick or stone or other material and by thecontribution provided by the strength of the binder used, also by meansof laboratory tests.

Once the building has been completed, as time goes by, the bed of binderthat is interposed between the blocks or part of the blocks themselvescan be disaggregated by the surrounding action produced by water or airor other agents, or can be conveyed elsewhere by filtering streams orcan be altered by the chemical action induced by various phenomena,including atmospheric ones.

This reduction of material within the wall cross-section causes thepresence of voids of various sizes, with a consequent net reduction ofthe effective resisting cross-section, a reduction in the allowabletension or an increase in permeability and other effects.

In some cases, this reduction in strength can cause the collapse of thebuilding.

In other cases, entirely intact wall systems which however contain voidsmight no longer perform their function correctly because they aresubjected to boundary or limit conditions that were not planned forduring design, such as for example the generation of tensions affectingthe wall system with a different intensity or direction with respect tothe design, or the presence of fluid adjacent to the walls of the wallsystems, with consequent filtering motions between the blocks, or theneed for greater thermal insulation on the part of the wall system, orthe need to improve the cohesion of the wall structure, or otherconditions.

Various systems are known for ensuring in any case the securing of themasonry and its regeneration. These are generally systems that tend torebuild the wall body by means of so-called “stitch and unstitch”operations, i.e., delicate operations that consist in partial removalsof deteriorated bodies, combined with temporary supports of thecomplementary masonry with auxiliary structures such as props, boards,ties, or others and the complete replacement of the removed parts. Thismethod, in addition to being highly invasive, requires very longexecution times and very high costs.

Other wall consolidation systems are known which consist in “choking”,or “hooping”, or the like, the deteriorated masonry. These systemsprovide for the aid of auxiliary elements to ensure the recovery of thestrength of the wall body, such as for example props, ribs, bars orothers. These methods, in addition to being highly invasive, modify theoriginal structure and geometry of the wall body, introducing newmetallic elements or others that remain visible to the observer. Thecosts for the application of these methods are generally very high.

Moreover, other systems are known which provide for the injection,horizontally or in any case at right angles to the two larger oppositefaces, in the wall system, of cement or chemical mixtures, possibly withadditives, in order to fill the voids that have formed. The injectionsperformed horizontally and at right angles to the surface of the wall,in order to ensure that all the voids are reached, must be verynumerous, also for the reasons that will become better apparenthereinafter, and therefore the procedure becomes long and onerous.Moreover, the mixtures used, which generally do not expand or haveextremely low degrees of expansion, are injected at low pressure byusing electric pumps or other devices or by gravity, most of all toavoid the risk of damaging the walls irreversibly. In the methodsdescribed above, therefore, a non-expanding or low-expanding material isused which, again to avoid damaging the wall system irreversibly, has anegligible expansion force (which may even not be known) that is most ofall uncontrolled and impossible to dissipate.

For all of these reasons, with these methods it is very difficult toensure both the filling of the all the voids, including the ones locatedfurthest from the injection point, and the complete filling ofvertically extended cavities. Finally, indeed because of the citedcharacteristics, these methods are unable to induce in the masonry astate of tension whereby the mechanical characteristics of the wallsystem are improved considerably with respect to the situation prior tothe intervention.

SUMMARY OF THE INVENTION

The aim of the present invention is to provide a method that allows torepair and/or waterproof and/or insulate and reinforce and/or restorethe structural integrity of wall systems effectively and durably andwith execution costs that are distinctly lower than those of the systemscurrently in use.

Within this aim, an object of the invention is to provide a method thatcan be adopted without problems even if the wall system or part thereofis immersed in water.

Another object of the invention is to provide a method that does notrequire the complete replacement of the elements that constitute thedeteriorated wall system and does not provide for the use of auxiliarystructures, including visible ones, suitable to increase the allowablestrength of the system or the resisting cross-section of said masonry ordecrease its permeability.

Another object of the invention is to provide a method that is simpleand rapid to perform, ensures the safety of the building during andafter the execution of the method, allows to reconstitute the structuralintegrity of the wall system, and ensures a distinct decrease in thepermeability of the wall system and/or ensures a reduction in itsthermal conductivity.

This aim and these and other objects that will become better apparenthereinafter are achieved by a method for repairing and/or waterproofingand/or insulating and/or reinforcing and/or restoring the structuralintegrity of wall systems, characterized in that it consists:

-   -   in providing spaced injection holes within a wall system in a        manner suitable to pass through cavities that exist in the wall        system;    -   in inserting injection tubes in said injection holes;    -   in injecting in said injection holes, through said injection        tubes, a substance that expands after injection as a consequence        of a chemical reaction.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomebetter apparent from the description of a preferred but not exclusiveembodiment of the method according to the invention, illustrated only byway of non-limitative example in the accompanying drawings, wherein:

FIG. 1 is a schematic view showing injection of the expanding substancethrough an injection hole formed in a wall system;

FIG. 2 is a schematic view illustrating the result of the expansion andconsolidation of the expanding substance if it is injected while theinjection tube is gradually retracted upward along the correspondinginjection hole;

FIG. 3 is a schematic view illustrating the result of the expansion andconsolidation of the expanding substance if it is injected withoutretracting the tube;

FIG. 4 is a view illustrating the result of the expansion of theinjected substance in the case of injections in multiple injection holesformed along the extension of a fractured wall system;

FIGS. 5, 6 and 7 are views illustrating treatment methods prior toinjection if the wall system has large cavities that lead to the outsideof the wall system;

FIG. 8 is a view illustrating the monitoring of the injection achievedby introducing in the wall system piezometer pipes filled with water.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the cited figures, the method according to theinvention substantially consists in producing, in a wall system 1 thatcontains voids or cavities 2, injection holes 3 which are spaced andwhose number varies according to the requirements and the conditions ofdeterioration of the wall system 1.

The injection holes 3 preferably run along directions that aresubstantially perpendicular to the surface of maximum extension of thecavities 2 inside the wall system 1.

If, as occurs more frequently, the wall system 1 is extended vertically,the injection holes 3 are preferably produced with a direction that isvertical or slightly inclined with respect to the vertical, since, as ithas been assessed, the larger cavities 2 inside the wall system 1 aregenerally arranged horizontally (for example a wall of bricks), so as tobe able to pass through the largest possible number thereof with everysingle injection hole 3. Said injection holes 3 can be provided directlyin the wall system 1, selectively, with different lengths according tothe specific requirements established on the basis of previous study ofthe structure and preferably with a distance between two contiguousinjection holes that can vary between 0.20 and 2.00 m.

The injection holes 3 can have variable dimensions according to thespecific requirements, in any case with a diameter preferably comprisedbetween 4 mm and 40 mm. In some cases it may be necessary to provide theinjection holes 3 in a direction other than vertical but in any casebetween the planes of arrangement of the two larger opposite faces ofthe wall system 1.

The depth of the injection holes 3 also can vary according to thespecific requirements, as will become better apparent hereinafter.

Injection tubes 4 are then inserted or driven into the injection holes3; said tubes are made of copper, PVC, steel or other material, and aresuitably constituted by and/or treated with lubricating material inorder to facilitate their sliding along the corresponding injection hole3.

Then a selected substance 5, called hereinafter “substance” that expandsafter injection by chemical reaction is injected through the injectiontubes 4 into the wall system 1.

Preferably, during the injection the injection tubes 4 are graduallyretracted along the corresponding injection hole 3 in the oppositedirection with respect to the direction of insertion, so that thesubstance 5 distributes in the plurality of cavities 2 that theinjection hole 3 passes through or are connected thereto, with thepurpose of involving, with a single operation, a vast volume of wallsystem 1 and of filling with the substance 5 a plurality of voids,interstices and cavities.

In the most frequent case of a wall system 1 that is extended verticallyand therefore has injection holes 3 that run vertically or are slightlyinclined with respect to the vertical, the injection tubes 3 aregradually retracted upward, during the injection of the substance 5, ata rate that is preferably variable, as will become better apparenthereinafter.

The selected substance 5, once injected, as a consequence of a chemicalreaction among its components, expands with a potential volume increasecomprised between 2 and 5 times the volume of the substance beforeexpansion and generates a maximum expansion pressure in conditions ofcomplete confinement that is normally comprised between 20 kPa and 200kPa, and is in any case selected to be always lower than the burstinglimit pressure of the wall system 1 being treated.

The maximum expansion pressure of said substance 5, as it has beenestablished by way of studies carried out while devising the presentmethod, greatly decreases for a minimal increase in volume of saidsubstance as a consequence of the chemical reaction, and so as toensure, if completely confined within a saturated wall cavity, aconsiderable reduction of the expansion pressure after minimal expansionand therefore after any minimal and tolerable deformations of thesurrounding wall elements. In particular, it has been established thatsaid substance has a strong reduction in maximum expansion pressurefollowing an expansion thereof of even less than 5% of its initialvolume. The term “dissipable” used in the present document, in thisconnection, is intended to express the mentioned concept.

The used, selected substance 5, before expansion, has a permeabilitycoefficient preferably equal to 10-9 m/s.

The substance 5 has, before the beginning of the chemical expansionreaction, an average viscosity comprised between 200 mPa·s and 300 mPa·sat 20° C. and in any case suitable to ensure the easy permeation of thecavities that can be reached by it as its exits from the injection tube4 in the wall system 1.

The substance 5 has a reaction time, i.e., the time interval between itsintroduction in the injection tube 4 and the beginning of the expansionprocess, that is normally comprised between 3 seconds and 60 seconds soas to avoid, depending on the thickness and characteristics of the wallsystem 1 to be subjected to the intervention, both an excessive escapeof the substance 5 from the treated masonry and a partial permeation ofthe voids that are present inside the wall system 1.

Directly after the beginning of the expansion process, the substance 5rapidly increases its viscosity until it becomes solid, i.e., with aviscosity that tends to infinity, once the reaction has ended; this timeperiod is preferably comprised between 20 and 150 seconds.

This characteristic is very important, also because it allows to injectthe substance 5 even into wall systems in direct contact with movingwater without the risk of washing it away and therefore conveying it outof the wall system. Moreover, said substance 5 is capable of performingregular expansion regardless of the presence of surrounding water.

Once it has expanded and consolidated, the substance 5 cannot be alteredby the presence of water, even if said water contains acids and/or richin sulfates and/or carbonates and/or salts in general.

Once consolidation has occurred, the substance 5 has good mechanicalcharacteristics, at least equal to those of the disaggregated materialthat the substance 5 has replaced. These mechanical characteristics canbe defined beforehand, within a certain margin, since they depend on thedensity of said substance 5 after expansion, which is directly afunction of the density of the substance 5 expanded in free air and ofthe amount of substance introduced during the injection step.

In particular, said substance 5, once it has consolidated, preferably,is selected so as to have a tensile strength substantially between anaverage of 180 N/cm² at a density of 200 kg/m³ and 800 N/cm² at adensity of 500 kg/m³, and a compression strength substantially betweenan average of 200 N/cm² at a density of 200 kg/m³ and 1300 N/cm² at adensity of 500 kg/m³, a property whereby it improves the mechanicalcharacteristics of the treated wall system 1 even with respect to itsoriginal conditions, especially if one considers that usually thedensity of the injected and consolidated substance 5 is higher than 500kg/m³ and therefore its tensile strength and compression strength areeven higher than indicated above, while the tensile strength ofconventional binders is practically zero.

The substance 5, once it has expanded and consolidated, has a lowerrelative density than water.

The selected substance 5 is conveniently constituted by a mixture ofexpanding polyurethane foam, preferably a closed-cell polyurethane foam.Said substance 5 can be constituted, for example, by a two-part(component) foam that is mixed inside a mixing unit of a known type, notshown for the sake of simplicity, which is connected to the injectiontubes 4 and is served by a pump that ensures the pressure required toinject the substance through the injection tubes 4. The first componentcan be a mixture of polyols comprising a polyether polyol, a catalystand water, such as that available under the name Uretek Hydro CP 200 Amanufactured by the Dutch company Resina Chemie. The second componentcan be an MDI isocyanate, such as that available under the name UretekHydro CP 200 B manufactured by the same company. The mixing of these twocomponents produces an expanding polyurethane foam whose density, at theend of expansion in free air (i.e., without confinement), is at leastequal to 200 kg/m³ and varies according to the volume of the cavities 2that are present in the wall system 1 and to the resistance opposed bythe walls that delimit said cavities 2.

Clearly, it is also possible to use other expanding substances that havesimilar properties without thereby abandoning the scope of theprotection of the present invention.

According to the requirements, the substance 5 can be injected, throughthe injection tubes 4 inserted in the injection holes 3, formedbeforehand in the wall system 1, in a single injection step or,selectively, with partial interruptions, as shown in FIGS. 1, 2 and 4,starting from below, while the injection tube 4 is gradually retractedupward at a rate that is preferably adjusted according to the pressureand/or flow-rate of injection of the substance 5.

If necessary, the substance 5 can also be introduced selectively byperforming localized injections in specific points of the wall system 1selected by appropriate engineering criteria, for example, where thereis a greater presence of voids or where there are water infiltrations,or where there is a structural discontinuity or other condition. In thislast case, the injection tubes 4 are not necessarily retracted but canbe left inside the wall system 1, as shown in FIG. 3. In this case also,it can be useful to measure the pressure and/or flow-rate of injectionof the substance 5 in order to check that the cavities 2 are filledcompletely and therefore decide to interrupt the injection.

The pressure and flow-rate of injection can be measured constantly bymeans of a monitoring system that comprises a pressure gauge and/or aflow-rate measurement device 6 of a known type, which are shownschematically for the sake of simplicity and are arranged upstream ofthe inlet of the injection tube 4 between said inlet and the mixer, forexample on an injection nozzle 7, of a known type, of an injectiondevice 8, that connects the mixer to the corresponding injection tube 4,so as to achieve complete filling of the cavities 2 before starting theretraction of the injection tube 4 or interrupting the injection of thesubstance 5.

In particular, an example is given of the importance of the use ofinjection monitoring by means of the instruments 6 cited above arrangedon the injection nozzle 7. This example is given merely by way ofnon-limitative indication: assuming that the characteristics of theintact wall system are already measured and known, so that the maximumpressure that can be withstood by the masonry, i.e., the limit burstingpressure (20 bar) divided by the safety coefficient (10), is 2 bar, theinjection process is selectively performed by limiting the injectionpressures in the steady state between 0 and 2 bar.

As the injection pressures measured by the pressure gauge 6 vary, theretraction rate of the injection tube 4 varies proportionally.

When the pressure measured by the pressure gauge located on theinjection nozzle is 0 bar, the injection tube 4 is retracted at the rateof 0 meters per minute; when the pressure measured by the pressure gaugelocated on the injection nozzle tends to, but is in any case lower than,2 bar, the injection tube 4 is retracted at the rate of 3 meters perminute; when the pressures measured by the pressure gauge located on theinjection nozzle are between 0 and 2 bar, the retraction rate of theinjection tube 4 varies proportionally between 0 and 3 meters perminute. The parameters described above, by way of example, can be variedeven considerably as a function of the characteristics of the wallsystem 1 that vary.

If a prolonged induction of overpressure occurs suddenly andinstantaneously and is measured by the pressure gauge 6 located on theinjection nozzle up to 10 bar (a value that is in any case lower thanthe bursting limit pressure of the masonry) and/or if a substantialdecrease or stoppage in delivery measured by the flow-rate measurementdevice occurs, a safety valve 12 or the like stops the injection streamthrough the feeding tube 14 that exits from the injection nozzle,deactivating the system and therefore the injection of the substance 5.The induction of overpressure must be prolonged and must last generallybetween 2 and 10 seconds, depending on the type of masonry. For veryrapid overpressure peaks (generally shorter than 2-10 seconds), it hasbeen observed that the masonry is in any case capable of toleratingcertain pressures, which are in any case lower than the bursting limitpressure, without necessarily undergoing deformation. In some cases,moreover, the occurrence of overpressure peaks helps to achieve morecomplete permeation of the voids on the part of the substance 5 in thewall system. It has been established that for substances whose viscosityis higher than the preferred viscosity cited above, the induction ofoverpressure produces very small benefits of higher permeation, offsetby high risks of bursting the wall system.

In the manner described, maximum safety is ensured and risks of collapseof the wall system are avoided, ensuring complete permeation thereof.

The flow-rate measurement device and the pressure gauge furthermoreallow to manage the injection, avoiding excessive outflows of thesubstance 5 from the wall system 1; if the dispensed flow-rate isexcessively high, the injection can in fact be interrupted, checking thewall system visually or with destructive or non-destructive tests inorder to determine whether there are excessive dispersions of thesubstance 5 outside the wall system 1.

This selectable system to be used to control continuously the injectionand retraction rate of the injection tubes 4 can be of the programmabletype, so that it can be applied to wall systems that have differentcharacteristics.

The injection tubes 4 have, at one of their axial ends, an inlet that isdesigned to be connected to the injection nozzle 7 and, at or proximateto their opposite axial end, one or preferably a plurality of outlets 9for the substance 5. In the case of multiple outlets, the sum of theindividual passage sections of said outlets is preferably larger thanthe passage section of the inlet to which the injection nozzle isapplied. This characteristic produces, among other effects, a greateruniformity of distribution of the substance 5 in the wall system 1, alower risk of sudden increases in pressure caused by obstruction of theinjection duct, constituted by the injection tube 4 and/or by theinjection hole 3, or by the filling of sealed cavities present in saidwall system and a reduction in the outflow rate of the substance 5 fromthe injection duct, with a consequent reduction of the risk of escapefrom the wall system 1.

Once injected, solely with the pressure induced by the pump, thesubstance 5, owing to its low viscosity (whose preferred values arecited above) tends to enter, before expansion, all the cavities 2 thatare more easily accessible in the wall system and expansion starts. Thisbehavior causes the controlled filling of the occupied cavities 2 andpropels the substance 5 further into the less accessible cavities,consequently filling them. The controlled and dissipable expansionpressure of the substance 5 avoids significant and dangerous breakagesand deformations in the wall system 1. All the solid elements thatconstitute the wall system 1 that surrounds the injection hole aresurrounded by a film of expanded substance whose dimensions aresubstantially equal to those of the preceding empty interstices,assuredly placed under tension again. Any fluids that are present incavities of the wall system are expelled by the expansion pressure ofthe substance 5, and all the stone or brick blocks that constitute thesolid skeleton of the wall system are reaggregated without beingsubjected to excessive tensions. If the wall system is immersed in wateror in the ground below the water table level, an expanding substance isused which reacts independently of the presence of water and is notaltered by it during the expansion process or after consolidation hasoccurred. For example, the mentioned Uretek Hydro CP 200 A expandssolely by virtue of the water contained therein, since it is a halogenand totally devoid of propellant compounds such as CFCs, HFCs, HCFCs andCFs. In other words, the chemical reaction of expansion occurs withoutabsorbing water from the surrounding environment and therefore withoutbeing damaged by said water or most importantly boosted uncontrollablyin its expansion force. Moreover, said element derives from renewableand non-polluting material.

It should be noted, according to the present invention, that thesubstance 5 injected into the wall system according to an appropriatelydesigned geometric grid automatically seeks the cavities 2 that areeasier to reach during expansion. In this manner, the substancecontinues to occupy the cavities until they are saturated, consequentlycausing an overpressure and a reduction in flow-rate, which can beverified at all times by the monitoring system located at the injectionnozzle as described above.

Another monitoring operation that can be performed during use is themonitoring of any movements, along directions that are substantiallyperpendicular to the planes of arrangement of the two larger oppositefaces of the wall system and therefore horizontally, if the wall systemis vertical, undergone by the wall system or by the entire outer surfaceof the wall system during the injection of the substance 5. Thismonitoring is optionally performed by using laser levels or similarinstruments that are commercially available and are suitable to detectin real time and continuously any minimum movement of the surfaces ofsaid wall system.

In the presence of large or in any case appreciable cavities in the wallsystem that rise to the surface, it is possible to perform interventionsprior to the injection of the substance 5 into the wall system. Theseinterventions differ depending on whether the surface of the wall systemis in contact with the ground or is exposed, i.e., its surface is freeor immersed in water. In the first case it is possible to actbeforehand, according to a known type of technique, with injections ofexpanding substances 10 that have a high degree of expansion and a greatexpansion pressure along the surface of the wall system directly incontact with the ground, or in the ground at a distance that can varyfrom 0.20 m to 1.00 m from the surface, as shown in FIGS. 5 and 6, inorder to push the soil or the injected expanding system toward thecavities of the wall system in order to close and block the openingsthat are present therein and rise to the surface. In the second case, itis possible to act along the surface of the wall system affected by thesurfacing of the cavities, for example by applying a sheet of geotextilematerial 11 or other material and by “spray” covering it by usingexpanding substances with a high degree of expansion and rapidhardening, as shown in FIG. 7. All this can be removed rapidlyimmediately after the operation for injection into the wall system. Toachieve the goal of confinement of the wall system, it is optionallypossible to use other methods, so long as they are capable of confiningany escape of the substance 5 from the cavities that reach the surfaceof the wall system.

In order to define precisely the center distance for performing theinjections in the masonry, it is possible to use the system shown inFIG. 8, i.e., the method of monitoring the injection performed byintroducing closed-end flexible and deformable piezometer pipes 13 intomeasurement holes 15 made in the wall system 1 in the vicinity of theinjection tube 4. Said piezometer pipes 13 are filled with water, andthe level of the water is visible in the portion of the piezometer pipes13 that protrudes upward from the wall system 1. The substance 5, duringthe filling of the cavities 2 that contain the piezometer pipes 13, byway of its expansion pressure, presses the walls of the piezometer pipes13, causing the rise of the level of the water contained therein. Thisnon-destructive monitoring allows to identify the space covered by theexpanding substance inside the wall system and to design accordingly thecenter distance of intervention required to consolidate said wallsystem.

This non-destructive monitoring system can be used systematically duringthe injection operations where it is important to check that the wallsystem has been permeated by the substance 5 in every cavity.

At the end of the treatment, it is possible to apply to the wall systemconventional integrity testing methods, either destructive ones such ascoring or others or non-destructive ones such as ultrasound testing orothers.

In practice it has been found that the method according to the inventionfully achieves the intended aim, since it allows, in a simple, rapid,effective, permanent, non-destructive and low-cost manner, to restorethe structural integrity of deteriorated wall systems, even in thepresence of water, in order to increase their mechanicalcharacteristics, reduce their permeability to water flows, reduce theirthermal conductivity, and other effects.

The method thus conceived is susceptible of numerous modifications andvariations, all of which are within the scope of the appended claims;all the details may further be replaced with other technicallyequivalent elements.

The disclosures in Italian Patent Application No. MI2002A001995 fromwhich this application claims priority are incorporated herein byreference.

1. A method for repairing and/or waterproofing and/or insulating and/orreinforcing a wall system by restoring the structural integrity thereof,the wall system comprising a solid aggregate structure consisting ofblocks of material with a binder interposed therebetween, the solidstructure extending between planes of arrangenment of opposite surfacesthereof, the method consisting: in locating cavities that exist and areformed in said solid structure by disaggregation of the block materialor binder; in providing spaced injection holes within said wall systemin a manner suitable to pass through said cavities that exist in thesolid structure; in inserting injection tubes in said injection holes;in injecting in said injection holes, through said injection tubes, asubstance that expands after injection as a consequence of a chemicalreaction, fills said cavities and restores the structural integrity ofthe solid structure.
 2. The method according to claim 1, wherein duringinjection said injection tubes are retracted gradually, in the oppositedirection with respect to insertion, along the corresponding injectionholes in order to allow said substance to penetrate the cavities crossedby, or proximate to, said injection holes.
 3. The method according toclaim 2, wherein said injection tubes are constituted by, or treatedwith, lubricating material in order to facilitate retraction thereofduring injection of said substance.
 4. The method according to claim 2,comprising during the injection of said substance, adjusting a rate ofrefraction of the injection tubes according to a pressure and/orflow-rate of injection of said substance.
 5. The method according toclaim 4, wherein the injection pressure is measured by way of a pressuregauge that is arranged upstream of the inlet of said injection tubes andis connected to the feeding tube for injection of said substance.
 6. Themethod according to claim 4, wherein the injection flow-rate is measuredby means of a flow-rate measurement device that is arranged upstream ofthe inlet of said injection tubes and is connected to the tube forfeeding the injection of said substance.
 7. The method according toclaim 4, comprising detecting presence of said substance and thepressure applied thereby during expansion at regions of the solidstructure of the wall system that are proximate to regions affected bythe injection.
 8. The method according to claim 7, comprising measuringthe presence of said substance and the pressure applied thereby duringexpansion, in the regions of the solid structure of the wall system thatare proximate to the regions affected by the injection, by way ofpiezometer pipes inserted in measurement holes provided in the wallsystem at preset distances from the injection holes in which saidinjection tubes are inserted.
 9. The method according to claim 1,wherein said injection holes are formed substantially at right angles tothe largest surface of the cavities inside the wall system.
 10. Themethod according to claim 1, wherein said substance is constituted by aclosed-cell polyurethane foam.
 11. The method according to claim 1,wherein said substance is constituted by an MDI i.e. a methylenediphenyl diisocyanate and a mixture of polyols.
 12. The method accordingto claim 1, wherein said substance has a maximum expansion pressuresubstantially comprised between 20 kPa and 200 kPa.
 13. The methodaccording to claim 12, wherein said substance has, during expansion, areduction in the maximum expansion pressure upon a low increase involume, i.e. a dissipation after a degree of expansion thereof that maybe less than 5% of its initial volume.
 14. The method according to claim1, wherein said substance has a maximum expansion pressure that is lowerthan a bursting limit pressure of the solid structure of the wall systemin which it is injected.
 15. The method according to claim 1, whereinthe reaction time of said substance is comprised between 3 and 60seconds.
 16. The method according to claim 1, wherein the chemicalreaction for expansion of said substance and said substance duringexpansion remain non-altered by water presence.
 17. The method accordingto claim 16, wherein said substance, once injected and hardened, has alower relative density than water.
 18. The method according to claim 1,wherein said substance, once expanded and consolidated, maintains anon-altered state in the presence of water, or water containing acidand/or water rich in sulfates and/or carbonates or salts in general. 19.The method according to claim 1, wherein said substance, once injectedand hardened, has a tensile strength substantially comprised between anaverage of 180 N/cm² at a density of 200 kg/m³ and 800 N/cm² at adensity of 500 kg/m³.
 20. The method according to claim 1, wherein saidsubstance, once injected and hardened, has a compression strengthsubstantially comprised between an average of 200 N/cm² at a density of200 kg/m³ and 1300 N/cm² at a density of 500 kg/m³.
 21. The methodaccording to claim 1, wherein said substance, prior to the beginning ofthe chemical reaction of expansion, has a viscosity substantiallycomprised between 200 mPa·s and 300 mPa·s at 20° C.
 22. The methodaccording to claim 21, wherein viscosity of said substance passes from avalue of 200-300 mPa·s to a value that tends to infinity in a timeinterval comprised between 20 and 150 seconds starting from thebeginning of the chemical reaction of expansion of said substance. 23.The method according to claim 1, wherein said injection holes areproduced along substantially vertical directions, and in that saidsubstance is injected through said injection tubes by graduallyretracting said injection tubes upward.
 24. The method according toclaim 1, wherein said injection holes are produced along directions thatare inclined with respect to the vertical and in that the injectionthrough said injection tubes is performed while gradually retractingsaid injection tubes upward.
 25. The method according to claim 1,wherein said injection holes are provided along a direction with alongitudinal extension that is contained between the planes ofarrangement of two opposite faces of the wall system.
 26. The methodaccording to claim 1, wherein the distance between two contiguousinjection holes is substantially comprised between 0.20 m and 2.00 m.27. The method according to claim 1, wherein a diameter of saidinjection holes is substantially comprised between 4 mm and 40 mm. 28.The method according to claim 1, wherein said injection tubes have aninlet that is connected to an injection device and multiple outlets forpassage of said substance.
 29. The method according to claim 28, whereinthe overall passage section of said outlets of said injection tubes isgreater than the passage section of said inlet.
 30. The method accordingto claim 1, comprising providing means for interrupting the injection ofsaid substance.
 31. The method according to claim 1, comprisingconstantly monitoring during the injection of said substance themovement of the solid structure of the wall system along directions thatare substantially perpendicular to the planes of arrangement of twolarger faces of the solid structure of the wall system.
 32. The methodaccording to claim 31, comprising following by way of a monitoringdevice with laser levels the movement of the solid structure of the wallsystem along directions that are substantially perpendicular to theplanes of arrangement of the two larger faces of the solid structure ofthe wall system.
 33. The method according to claim 1, comprisingpreliminary interventions to limit escape of said substance from outletsof said cavities that lead out of the solid structure of the wallsystem.
 34. The method according to claim 33, wherein said preliminaryinterventions consist in performing column-type injections of asubstance that expands by chemical reaction in the soil directly in theinterface between the soil and the wail system and/or in regions of theground that are spaced from the wall system.
 35. The method according toclaim 33, wherein said preliminary interventions consist in applying asheet of geotextile fabric to the surface of the solid structure of thewall system where said outlets of the cavities are present and inperforming a spray covering of said fabric with a substance that expandsby chemical reaction.
 36. A method for repairing, waterproofing,insulating and reinforcing a wall system by restoring structuralintegrity thereof, the wall system comprising a solid aggregatestructure consisting of blocks of material with a binder interposedtherebetween, the solid structure extending between planes ofarrangement of opposite surfaces thereof, the method consisting: inlocating existing cavities formed in said solid structure bydisaggregation of the block material or binder; in providing spacedinjection holes that extend along substantially vertical directionswithin said solid structure of the wall system in a manner suitable topass through said cavities that exist in the solid structure; ininserting injection tubes in said injection holes; in injecting in saidinjection holes, through said injection tubes which are graduallyretracted upward during injection, a substance that expands afterinjection as a consequence of a chemical reaction, fills said cavitiesand the injection holes and restores the structural integrity of thesolid structure.
 37. A method for repairing, waterproofing, insulatingand reinforcing a wall system by restoring structural integrity thereof,the wall system comprising a solid aggregate structure consisting ofblocks of material with a binder interposed therebetween, the solidstructure extending between planes of arrangement of opposite surfacesthereof, the method consisting: in locating existing cavities formed insaid solid structure by disaggregation of the block material or binder;in providing spaced injection holes that extend along substantiallyvertical directions within said solid structure of the wall system in amanner suitable to pass through said cavities that exist in the solidstructure; in selecting an expandable substance suitable to expand as aconsequence of a chemical reaction that before expansion has apermeability coefficient equal to 10-9 m/s and an average viscositycomprised between 200 and 300 in mPa·s at 20° C.; in inserting injectiontubes in said injection holes; in injecting in said injection boles,through said injection tubes which are gradually refracted upward duringinjection, a substance that expands after injection as a consequence ofa chemical reaction, fills said cavities and the injection holes andrestores the structural integrity of the solid structure.